The last function in sat-solve-7’s body is:
```scheme
(lambda (n7)
((((((p n1) n2) n3) n4) n5) n6) n7)
```
Because of all the parentheses, it’s hard to see, but this is actually the following:
```scheme
(lambda (n7)
((((((p n1) n2) n3) n4) n5) n6)
n7)
```
This function is applying the predicate `p` with only the first six arguments. Then it discards the result and outputs `n7`, as is. It’s a convoluted identity function!
The fix is to add yet more parenthesis:
```scheme
(lambda (n7)
(((((((p n1) n2) n3) n4) n5) n6) n7))
```